Lawmakers should craft legislation to close a loophole in guns laws through which unlicensed sellers can peddle weapons to buyers without background checks.

Had such a law been in place, it might have kept kept a gun out of the hands of Radcliffe Haughton and saved the lives of three women at the Azana Salon & Spa in Brookfield.

Yes, it seems apparent now that Haughton was bent on killing his estranged wife. And he may well have found another way to get a gun. But that doesn't mean that such legislation would not keep guns out of the hands of others who buy them every year without undergoing a background check.

The proposal was resurrected by Milwaukee Mayor Tom Barrett and is supported by the Brady Center to Prevent Gun Violence, an advocacy group based in Washington, D.C.

About 40% of all legal gun sales in the nation require no background check, which is an open floodgate through which thousands of weapons flow to criminals, people with mental illness and domestic abusers. Radcliffe was subject of a restraining order and had been ordered to turn over his guns to authorities days before his shooting rampage. Radcliffe's wife, Zina, was granted a four-year restraining order against her husband because she said she feared for her life. She died along with two others; four were hurt in the mass shooting on Oct. 21.

The couple had a volatile relationship. Police had been to their Brown Deer home on 20 different occasions. These red flags should not have been ignored, but they were.

Days after Zina Haughton was granted the restraining order, her husband posted a "gun wanted" ad on a website. The ad read:

"Looking for a handgun that is $300 or best offer. Looking to buy ASAP. Prefer full size. Prefer 45 or 40 caliber. I constantly check emails. Also I'm hoping to has a high mag capacity. I'm a serious buyer so please email me ASAP. Have cash now and looking to buy now."

Barrett's proposal would force all buyers to abide by a mandatory waiting period and to go through a background check at a licensed dealer.

This would not keep a gun out of the hands of everyone who should not have one, but it could stop some. The state should not make it easier for them to get their hands on weapons.

For legal gun owners and sellers, a change in the law will be a slight inconvenience. They may have to wait at most two days before they can get their gun. That's a small price to pay if it can prevent a tragedy.

We know some will argue that such a proposal infringes on their Second Amendment right to own a gun. But a background check has nothing to do with the Second Amendment. This is, in fact, one more way to keep the public safe.